Brazing , Soldering & Adhesive Bonding

Brazing , Soldering & Adhesive Bonding

1. Brazing and soldering differ from fusion welding because no melting the base metal occurs

2. Brazing and soldering differ from fusion welding because no melting the base metal occurs

3. In brazing the filler metal melts at a temperature above 450C (840F). In soldering the filler metal melts at a temperature of 450C or below.

4. Brazing or soldering might be preferred over welding if (1) the base metals have poor weldability, (2) the components cannot tolerate the higher heat and temperatures of welding, (3) production rates need to be faster and less expensive than welding, (4) joint areas are inaccessible for welding but brazing or soldering is possible, and (5) the high strength of a welded joint is not a requirement.

5. Brazing

   • The two joint types most commonly used in brazing are butt and lap joints.
   • characteristics are needed for filler metal :
     • melting temperature must be compatible with the base metal
     • surface tension in the liquid phase must be low for good wettability
     • fluidity of the molten metal must be high for penetration into the interface
     • the metal must be capable of being brazed into a joint of adequate strength for the application
     • chemical and physical interactions with base metal (e.g., galvanic reaction) must be avoided.
   • Jenis-jenis brazing berdasarkan sumber pemanasnya
     • Torch brazing
       • In torch brazing, flux is applied to the part surfaces and a torch is used to direct a flame against the work in the vicinity of the joint
       • Torch brazing is often performed manually
     • Furnance brazing
       • Furnace brazing uses a furnace to supply heat for brazing and is best suited to medium and high production.
     • Resistance brazing
       • Heat to melt the filler metal in this process is obtained by resistance to flow of electrical current through the parts.
     • Induction brazing
       • Induction brazing utilizes heat from electrical resistance to a high frequency current induced in the work.
         • The parts are preloaded with filler metal and placed in a high-frequency AC field—the parts do not directly contact the induction coil.
     • Dip brazing
       • Menyambungkan benda kerja dengan cara mencelupkan benda kerja ke larutan logam cair atau larutan garam di atas temperature cair logam
         • DB cocok untuk material berbentuk lembaran dan kawat.
   • disadvantages and limitations of brazing?
     • joint strength is generally less than that of a welded joint
     • high service temperatures may weaken a brazed joint
     • the color of the metal in the brazed joint may not match the color of the base metal parts
   • The strength of a brazed joint is typically stronger than the filler metal
   • Best clearances between surfaces in brazing are 0.025 to 0.250 mm
   • Advantages
     • dissimilar metals can be joined
     • less heat and energy required than fusion welding,
     • multiple joints can be brazed simultaneously
   • Flux
     • Characteristics of a good flux
       • protects the joint until solidification of the filler metal. The flux should also be easy to remove after brazing.
       • facilitates wetting
       • low viscosity so that it can be displaced by the filler metal
       • low melting temperature
     • function of a flux in brazing or soldering
       • promote wetting of the surfaces
       • protect the faying surfaces during the process
       • remove or inhibit formation of oxide films

6. Adhesive Bondng

   • Adhesive bonding is a joining process in which a fillermaterial is used to hold two (or more) closely spaced parts together by surface attachment.
     • The filler material that binds the parts together is the adhesive. It is a nonmetallic substance—usually a polymer
     • The parts being joined are called adherends
     • Curing refers to the process by which the adhesive’s physical properties are changed from a liquid to a solid
     • Stuctural adhesive adalah kapabalitas untuk membentuk suatu sambungan yang kuat dan kaku
   • limitations of adhesive bonding
     • Perekat relatif tidak lebih kuat dibanding jenis penyambungan lain
     • Curing time yang memakan waktu sehingga menurunkan kecepatan produksi
     • Adhesive must be compatible with adherend materials
     • Pemberian temperatur sangat terbatas
     • Permukaan benda yang disambung harus sangat bersih
     • Inspeksi kekuatan sulit dilakukan
   • Advantages
     • aplicable to wide variety of materials
     • Hanya perlu suhu rendah untuk merekatkan benda, sehingga tidak merusak
       • Dapat menyambungkan benda yang rapuh
     • Bonding terjadi pada seluruh permukaan sambungan karena lem lebih mudah tersebar merata(fluiditas tinggi)
     • Masih memungkinkan adanya peregangan setelah curing time
     • Bisa digunakan untuk penyegelan selain penyambung
   • Application Methods
     • Brushing
     • Flowing
     • Manual rollers
     • Silk screening
     • Spraying
     • Automatic applicators
     • Roll coating
   • precondition for the success of an adhesive bonding operation is cleanliness of adherend's surface
   • the three basic categories of commercial adhesives
     • natural adhesive
       • pati/zat tepung
       • collagen
     • inorganic adhesive
       • sodiium sillicate
     • Sythetic adhesive
       • thermoplastic polymer
       • thermosetting polymer
   • Metode memadatkan adhesive dari keadaan cair
     • Dengan menggunakan reaksi kimia antar dua jenis adhesive
     • Disinari sinar ultraviolet
     • Diberikan tekanan
     • Dipanaskan
   • Joint Design
     • The following design principles are applicable
       • Joint contact area should be maximized
       • • Adhesive joints are strongest in shear and tension
         • bonded joints are weakest in cleavage or peeling

7. Soldering

   • the disadvantages and drawbacks of soldering
     • Kenaikan temperatur dapat melemahkan sambungan
     • Kekuatan sambungan lemah jika tidak diperkuat
   • Advantages
     • low energy input relative to brazing and fusion welding
     • various heating methods available
     • good electrical and thermal conductivity of the joint
       • Sehingga banyak diaplikasikan dikomponen-komponen komputer
     • ease of repair and rework
     • capable of making air-tight and liquid-tight joints
   • SOLDERING METHODS
     • Wave soldering
       • Wave soldering is a mechanized technique that allows multiple lead wires to be soldered to a printed circuit board (PCB) as it passes over a wave of molten solder
       • Wave soldering is widely applied in electronics to produce printed circuit board assemblies
     • Hand Soldering
       • Hand soldering is performed manually using a hot soldering iron
       • A bit, made of copper, is the working end of a soldering iron
         • Its functions are
           • to deliver heat to the parts being soldered,
           • to melt the solder
           • to convey molten solder to the joint
     • Reflow Soldering
       • This process is also widely used in electronics to assemble surface mount components to printed circuit boards
       • Heating method
         • vapor phase reflow soldering
           • inert fluorinated hydrocarbon liquid is vaporized by heating in an oven; it subsequently condenses on the board surface where it transfers its heat of vaporization to melt the solder paste and form solder joints on the printed circuit boards.
         • infrared reflow soldering
           • heat from an infrared lamp is used to melt the solder paste and form joints between component leads and circuit areas on the board.
       • An emulsion is a mixture of two immiscible liquids (usually oil and water, in various proportions), along with additives.
   • following metals are used in solder alloys : timah(mostly),timbal(mostly),antimon dan perak

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